Cleaning freezers are part of the annual refrigerator cleaning, but what of chest freezers? They can get that funky freon smell, too, and if not defrosted every six months, they can collect frost on the seal causing the unit to have to work twice as hard to keep food frozen, resulting in higher electricity bills and freezer burn.
Remove all of the food, and place in small coolers or the refrigerator. Unplug the chest freezer and use a blow dryer on "high" or "hot" to speed the process. A large spackling knife and a hammer can be used to chip off the ice stuck on the side if you do it carefully. Slip the edge of the knife between the ice and the side of the freezer and tap gently with the hammer. Even better, do this at a time when there is little food in the freezer and let the ice melt on its own.
You can siphon out the melted water with a hose, but this is why the chipping method is faster, you don't need to siphon out melted ice, you can just pick out the chunks.
Unless ice cream spilled or you have dried meat blood in the bottom, you need only wash out the freezer with baking soda and warm water. Use as little water as possible so you can soak it up with a towel, there are few things worse than cleaning freezers by having to siphon out nasty water. Wipe the inside with old, dry towels and vacuum the condenser coils in the back. The brush attachment on your vacuum works well for this, as opposed to the suction stick for curtains.
Replace the food and plug the freezer back in. If there is a drip pan under the freezer, and there usually is, draw it out slowly and dump and clean with regular dish detergent and warm water. This is where some of the smell can come from, so sprinkling a little baking soda in the bottom before replacing it can't hurt. Wipe off the outside of the freezer like you would any other appliance.
To prevent odors and spillage, as well as freezer burn, wrap your frozen foods in plastic wrap and again in aluminum foil. This is an old cook's trick in the restaurant business. Cleaning freezers in a restaurant takes most of a shift, and loses valuable cooking time, so they came up with this to decrease spillage. The more air tight the containers, the fresher the food will keep, keep longer, and cleaning freezers takes only about half a shift. Plastic pans spread with baking soda on the bottom of the freezer will also help with stale smells. If you have a bad problem with chest freezer odor, it may be that you have a freon leak. This should be checked and fixed, but you can also buy activated charcoal to help eliminate really foul odors, such as the freezer accidentally being shut off after a power outage while you are on vacation.